1) Replaced is_insertable() field mehtod with readonly property (unification with model and tables)

2) Method SystemPart.all() was replaced with get()
3) Added conditions parameter to SystemPart.get() and SystemPart.get_active() methods.

README.rst

@@ -182,6 +182,29 @@ You can optionally pass conditions to the query::
 Note that ``order_by`` must be chosen so that the ordering is unique, otherwise there might be
 inconsistencies in the pagination (such as an instance that appears on two different pages).
 
+System models
+-------------
+`Clickhouse docs <https://clickhouse.yandex/reference_en.html#System tables>`
+System models are read only models for implementing part of the system's functionality,
+and for providing access to information about how the system is working.
+
+Usage example:
+
+    >>>> from infi.clickhouse_orm import system_models
+    >>>> print(system_models.SystemPart.all())
+
+Currently the fllowing system models are supported:
+
+===================  ========    =================  ===================================================
+Class                DB Table     Pythonic Type      Comments
+===================  ========    =================  ===================================================
+SystemPart
+
+Partitions and parts
+--------------------
+`ClickHouse docs <https://clickhouse.yandex/reference_en.html#Manipulations with partitions and parts>`
+
+
 Schema Migrations
 -----------------
 

src/infi/clickhouse_orm/fields.py

@@ -70,8 +70,9 @@ class Field(object):
         else:
             return self.db_type
 
-    def is_insertable(self):
-        return self.alias is None and self.materialized is None
+    @property
+    def readonly(self):
+        return self.alias is not None or self.materialized is not None
 
 
 class StringField(Field):

src/infi/clickhouse_orm/models.py

@@ -159,9 +159,8 @@ class Model(with_metaclass(ModelBase)):
         :param bool insertable_only: If True, returns only fields, that can be inserted into database
         '''
         data = self.__dict__
-        fields = self._fields
-        if insertable_only:
-            fields = [f for f in fields if f[1].is_insertable()]
+
+        fields = [f for f in self._fields if not f[1].readonly] if insertable_only else self._fields
         return '\t'.join(field.to_db_string(data[name], quote=False) for name, field in fields)
 
     def to_dict(self, insertable_only=False, field_names=None):
@@ -170,7 +169,7 @@ class Model(with_metaclass(ModelBase)):
         :param bool insertable_only: If True, returns only fields, that can be inserted into database
         :param field_names: An iterable of field names to return
         '''
-        fields = [f for f in self._fields if f[1].is_insertable()] if insertable_only else self._fields
+        fields = [f for f in self._fields if not f[1].readonly] if insertable_only else self._fields
         if field_names is not None:
             fields = [f for f in fields if f[0] in field_names]
 

src/infi/clickhouse_orm/system_models.py

@@ -113,25 +113,30 @@ class SystemPart(Model):
         return self._partition_operation_sql(database, 'FETCH', settings=settings, from_part=zookeeper_path)
 
     @classmethod
-    def get_active(cls, database):
+    def get(cls, database, conditions=""):
         """
-        Get all active parts
+        Get all data from system.parts table
         :param database: A database object to fetch data from.
+        :param conditions: WHERE clause conditions. Database condition is added automatically
         :return: A list of SystemPart objects
         """
         assert isinstance(database, Database), "database must be database.Database class instance"
+        assert isinstance(conditions, str), "conditions must be a string"
+        if conditions:
+            conditions += " AND"
         field_names = ','.join([f[0] for f in cls._fields])
-        return database.select("SELECT %s FROM %s WHERE active AND database='%s'" %
-                               (field_names,  cls.table_name(), database.db_name), model_class=cls)
+        return database.select("SELECT %s FROM %s WHERE %s database='%s'" %
+                               (field_names,  cls.table_name(), conditions, database.db_name), model_class=cls)
 
     @classmethod
-    def all(cls, database):
+    def get_active(cls, database, conditions=""):
         """
-        Gets all data from system.parts database
-        :param database:
-        :return:
+        Gets active data from system.parts table
+        :param database: A database object to fetch data from.
+        :param conditions: WHERE clause conditions. Database and active conditions are added automatically
+        :return: A list of SystemPart objects
         """
-        assert isinstance(database, Database), "database must be database.Database class instance"
-        field_names = ','.join([f[0] for f in cls._fields])
-        return database.select("SELECT %s FROM %s WHERE database='%s'" %
-                               (field_names, cls.table_name(), database.db_name), model_class=cls)
+        if conditions:
+            conditions += ' AND '
+        conditions += 'active'
+        return SystemPart.get(database, conditions=conditions)

tests/test_system_models.py

@@ -26,7 +26,7 @@ class SystemPartTest(unittest.TestCase):
         return dirnames
 
     def test_get_all(self):
-        parts = SystemPart.all(self.database)
+        parts = SystemPart.get(self.database)
         self.assertEqual(len(list(parts)), 1)
 
     def test_get_active(self):
@@ -35,6 +35,12 @@ class SystemPartTest(unittest.TestCase):
         parts[0].detach(self.database)
         self.assertEqual(len(list(SystemPart.get_active(self.database))), 0)
 
+    def test_get_conditions(self):
+        parts = list(SystemPart.get(self.database, conditions="table='testtable'"))
+        self.assertEqual(len(parts), 1)
+        parts = list(SystemPart.get(self.database, conditions="table='othertable'"))
+        self.assertEqual(len(parts), 0)
+
     def test_attach_detach(self):
         parts = list(SystemPart.get_active(self.database))
         self.assertEqual(len(parts), 1)
@@ -49,7 +55,7 @@ class SystemPartTest(unittest.TestCase):
         self.assertEqual(len(list(SystemPart.get_active(self.database))), 0)
 
     def test_freeze(self):
-        parts = list(SystemPart.all(self.database))
+        parts = list(SystemPart.get(self.database))
         # There can be other backups in the folder
         prev_backups = set(self._get_backups())
         parts[0].freeze(self.database)